Causes of Surface Water Pollution:

b. Oxygen depleting wastes: These are organic wastes that can be decomposed by aerobic bacteria. The amount of oxygen required to break down a certain amount of organic matter is called BOD. It is an indicator of level of pollution.

c. Inorganic plant nutrients: There are water soluble nitrates and phosphates.

d. Excess pesticides: For control of pest pesticides are used in discriminately. These fall on ground and leach with rain water to canals and rivers.

e. Water soluble organic chemicals: These are acids, salts and compounds of toxic metals such as mercury and lead.

f. Variety of organic chemicals: includes oil, gasoline, plastics, pesticides, detergents and many other chemicals.

g. The sediments of suspended matter: Occur when soil is eroded.

h. Water soluble radioactive isotopes: Enter the water courses along with rain water.

ADVERTISEMENTS:

i. Hot water released by power plants and industries that use large volume of water to cool the plant results in a rise in temp of local water bodies.

j. Acid drainage into rivers.

Causes of Ground Water Pollution:

A greater threat to human life comes from ground water which is used for drinking and irrigation being polluted.

a. Urban runoff of untreated or poorly treated waste water storage and garbage.

b. Industrial waste storage located above or near aquifer

c. Agricultural practices such as application of large amounts of fertilizers and pesticides, animal feeding operations etc. in rural sector

Effects of Water Pollution:

1. Large amount of human waste in water increase the number of bacteria such as Escherichia coli and streptococcus species which cause gastro intestinal diseases. Water bore diseases diarrhea, typhoid etc.

2. If more organic matter is added to water the O2 is used up. This causes fish and other forms of O2 dependent aquatic life dies.

3. Eutrophication due to inorganic pollutants:

Eutrophication The term “eutrophic” means well-nourished; thus, “eutrophication” refers to natural or artificial addition of nutrients to bodies of water and to the effects of the added nutrients. When the effects are undesirable, eutrophication may be considered a form of pollution (National Academy of Sciences, 1969).

Nixon (1995) defined it as an increase in the rate of supply of organic matter in an ecosystem. It is the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote excessive growth of algae.

As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Similarities include subsequent negative environmental effects such as anoxia, and severe reductions in water quality, fish and other animal populations may occur.

Other species may experience an increase in population that negatively affects other species in the direct ecosystem. In simpler terms it is the bloom of phytoplankton in a water body. It is often the result of anthropogenic pollution with nutrients, particularly the release of sewage effluent and agricultural run-off carrying fertilizers into natural waters.

However, it also occurs naturally in situations where nutrients accumulate (e.g., depositional environments) or where they flow into systems on an ephemeral basis. Eutrophication generally promotes excessive plant growth and decay, favours simple algae and plankton over other more complicated plants, and causes a severe reduction in water quality.

In aquatic environments, enhanced growth of choking aquatic vegetation or phytoplankton (e.g., algal blooms) disrupts normal functioning of the ecosystem, causing avariety of problems such as a lack of oxygen in the water, needed for fish and shellfish to survive. The water then becomes cloudy, coloured a shade of green, yellow, brown, or red.

Human society is impacted as well: eutrophication decreases the resource value of rivers, lakes, and estuaries such that recreation, fishing, hunting, and aesthetic enjoyment are hindered. Health-related problems can occur where eutrophic conditions interfere with drinking water treatment.

4. Bio-magnification due to excess use of pesticides:

Bio-magnification, also known as bio-amplification or biological magnification, is the increase in concentration of a substance, such as the pesticide DDT that occurs in a food chain as a consequence of:

a. Persistence (can’t be broken down by environmental processes)

b. Food chain energetic

Low (or nonexistent) rate of internal degradation/excretion of the substance (often due to water-insolubility). Biological Magnification often refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans.

The substances become concentrated in tissues or internal organs as they move up the chain. Bio-accumulates are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. For example, though mercury is only present in small amounts in sea water, it is absorbed by algae (generally as methyl mercury.

Bioaccumulation and bio-concentration result in buildup in the adipose tissue of successive trophic levels: zooplankton, small nekton, larger fish etc. Anything which eats these fish also consumes the higher level of mercury the fish have accumulated.

This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone. For example, herring contains mercury at approximately 0.01 ppm and shark contains mercury at greater than 1 ppm (EPA 1997).

5. High levels of organic chemicals (acids, salts and toxic metals) can make the water unfit to drink, harm fish and other aquatic life, reduce crop yields.

6. Variety of organic chemicals/oil gasoline, plastics detergents are harmful to aquatic life and human life.

7. Sediments (erosion) fish clog the lakes and artificial reservoirs.

8. Radioisotopes cause birth defects, cancer and genetic damage. Hot water cause thermal pollution not only decreases the solubility of O2 but also changes the breeding cycles of various aquatic organisms.

9. Hot water because of thermal pollution not only decreases the solubility of O2 but also changes the breeding cycles of various aquatic organisms.

13. Arsenic poisoning is the major effect mostly in West Bengal. Arsenicosis or arsenic toxicity develops after 2-5 years exposure to arsenic contaminated drinking water.

Control Measures of Water Pollution:

a. Setting up of effluent and sewage treatment plants to treat waste water can reduce the pollution load in the recipient water. The treated effluent and domestic water can be reused either for gardening or cooling purposes or wherever possible. Sewage treatment either removes the harmful components or converts them into harmless components.